A steel pipe made of a single piece of metal with no joints on the surface is called a seamless steel pipe. According to the production method, the hot rolled tube, the cold rolled tube, the cold drawn tube, the extruded tube, the top tube and the like are seamlessly divided. According to the shape of the cross-section, the seamless steel tube is divided into two types: round and irregular. The special-shaped tube has a variety of complex shapes such as square, oval, triangular, hexagonal, melon-shaped, star-shaped and finned tubes. The maximum diameter is 650mm and the minimum diameter is 0.3mm. According to different uses, there are thick-walled tubes and thin-walled tubes. Seamless steel tubes are mainly used as petroleum geological drilling tubes, cracking tubes for petrochemical industries, boiler tubes, bearing tubes, and high-precision structural steel tubes for automobiles, tractors, and aviation.
There are seamless steel tubes along the perimeter of its cross section. According to different production methods, it can be divided into hot-rolled tubes, cold-rolled tubes, cold-drawn tubes, extruded tubes, and top-tubes. Materials are common and high-quality carbon structural steel (Q215-A ~ Q275-A and 10 ~ 50 steel), low alloy steel (09MnV, 16Mn, etc.), alloy steel, stainless steel and other acid. Divided into general-purpose (for water, gas pipelines and structural parts, mechanical parts) and dedicated (for boilers, geological exploration, bearings, acid, etc.) by purpose.